This invention concerns an apparatus to regulate the illumination range of a motor vehicle having a front axle sender at a front wheel axle, a rear axle sender at a rear axle (output signals of the senders being a function of a relative position of a motor vehicle body to the wheel axles), a nominal-value former which forms a difference between the signals from the front axle sender and the rear axle sender, a first filter including an average-value former which, in dependence on a first filter time constant, develops filtered nominal-value signals from the unfiltered nominal-value signals of the nominal-value former, and a regulator which regulates adjusting elements to adjust positions of headlights.
An apparatus to regulate the illumination range of a motor vehicle of this type is disclosed in German Offenlegungsschrift DE OS 31 10 094 A1.
Sensors which measure the relative position of a motor vehicle body to motor vehicle axles or motor vehicle wheels are coupled to an analog-multiplexer which feeds the available signals from the sensors via an analog/digital converter to a microprocessor. A filtering of the appearing signals results in which, in a fixed time span, an average-value formation of the signals is carried out. In addition, the amount, or number, of the average values to be included is assumed or predetermined. From the average values then for each sensor pair corresponding to a front axle sensor and a rear axle sensor, a difference signal is formed that corresponds to a headlight adjustment value. Each of these difference signals is fed to a digital/analog converter which is respectively coupled over a subsequently coupled operational amplifier with a headlight adjusting device. In dependence upon a sign (+ or -) of the difference signal, the adjusting elements will be thereby moved forwardly or rearwardly and a headlight storage register in a microprocessor will count upwardly or downwardly.
This known apparatus has proven itself to be disadvantageous for the regulation of the illumination range of a motor vehicle in that the average value formation only occurs in a fixed time interval so that an adaptation to changing operating conditions of the motor vehicle cannot take place. In particular, upon braking the motor vehicle, which in a short time leads to great inclination changes of the motor vehicle body, the adjustment of the illumination range is not changed quickly enough to exclude a blinding of oncoming traffic and other losses of safety which can lead to dangerous situations upon operation of a motor vehicle. This is particularly true when, as with the known apparatus, for example, a filter time constant in a size range of around a minute is chosen so that upon braking, in particular upon strong braking, and as well as also after braking, the adjustment of the headlights, and thereby the illumination range of the motor vehicle, has false adjustments which can lead to dangerous situations.
Further, known apparatus have proven to be disadvantageous in that four sensors on wheel axles are provided which feed their signals over an analog-multiplexer to a processor because this results in a costly device which additionally, in an expensive manner, is cost intensive to manufacture and mount.
It is an object of this invention to provide an apparatus which, in an uncomplicated and cost-effective manner, without a travel, or road signal being present and analyzed, upon braking incidents of a motor vehicle, improves the dynamic of regulation of the illumination range.